The present invention relates to a method of surface cleaning articles by removing surface particulate matter from the articles. More particularly, the present invention relates to such a method in which the surface particulate matter is removed from the articles by the use of a liquid cryogen.
Unwanted surface particulate matter exists on articles either initially, by virtue of their manufacture, or after manufacture, during packaging, shipment, and use of the articles, by virtue of surface contamination. For instance, a common catalyst consists of pelletized material formed of nickel and silica. After the preparation of such a catalyst, small particles of nickel and silica are found on the surfaces of the pellets. Another example is pelletized adsorbents formed of carbon molecular sieve material, zeolite material, and etc. Often, such pelletized adsorbent is formed with small particles of the adsorbent clinging to the surfaces of the pellets. Additionally, small mechanical components, such as found in clockwork mechanisms and the like, gather particulate contaminants on their surfaces during use.
The surface particulate material is unwanted in the case of catalysts and adsorbents because when the adsorbent or catalyst is in use, the surface particulate matter can eventually plug valves, filters, etc. It goes without saying that surface particulate matter must be removed from mechanical components of mechanisms in order to insure the continued working of such mechanisms.
In the prior art, pelletized catalyst and adsorbent materials are cleaned by bed fluidization. In bed fluidization, a gas is sent through a bed containing such pelletized materials. The small surface particulate matter normally rises higher than the larger pellets to allow the particulate matter to be collected at the top of the bed in a bag house. Pelletized materials are also cleaned by shaking the materials over a screen. This latter method is ineffective and can damage the articles to be cleaned. Another prior art method of cleaning adsorbents, catalysts, as well as small mechanical components, is with solvents such as water. One problem here is that it is often difficult to dry the article after cleaning the article. Additionally, some adsorbents and catalysts may be damaged by solvents.
As contrasted with the prior art, the present invention provides a method of removing surface particulate matter from articles that is simpler, causes less damage, and is less expensive than prior art cleaning techniques and additionally, does not utilize solvents such as water.